Effects of fibrinogen supplementation on clot formation in blood samples from cardiac surgery patients before and after tranexamic acid administration

Abstract

To investigate if supplementation with fibrinogen concentrate to blood samples collected after tranexamic acid administration improve clot formation more than what can be achieved with fibrinogen in the absence of tranexamic acid. It is not known if the combination of fibrinogen and tranexamic acid has additional effects than what can be achieved individually. Four blood samples were collected from 15 coronary artery bypass patients. Two samples were collected before surgery, before and after 2g tranexamic acid was administered. The preoperative samples were diluted to haematocrit 21%. Two samples were collected after surgery, before and after a second dose of 2g tranexamic acid. Fibrinogen concentrate corresponding to a dose of 3g in a 70-kg patient was added to the samples. Platelet-independent clotting time and maximum clot firmness assessed by thromboelastometry (ROTEM-FIBTEM®) were compared between the samples. Administration of tranexamic acid shortened clotting time marginally (-6%) before surgery, P=0·029) but did not influence clot firmness. Fibrinogen concentrate shortened clotting time (-14% before and -12% after surgery, both P=0·003) and increased clot firmness (+51 and +39%, both P<0·001). The effects of fibrinogen did not differ before and after tranexamic acid administration. Fibrinolysis was not detected in any sample. The results of this in vitro study suggest that the enhancing effects of fibrinogen on clot firmness in blood samples from cardiac surgery patients are not further increased in the presence of tranexamic acid. Further studies on patients with ongoing bleeding and/or hyperfibrinolysis are necessary to validate the results.